Running Head: SEARCHING FOR LIFE
Searching for Life in Our Solar System
SEARCHING FOR LIFE
The search for life on other planets is one of the most exciting activities a scientist can
undertake. Confirmation of the existence of life on other planets would force humanity to rethink
its place in the universe and the role they play in it. The broader implications across the natural
sciences would be transformative. Improvements in technology are allowing us to study the
universe in greater depth. The progress in the field of astrobiology seems unstoppable, and it is
opening us to discoveries that just a few years ago, we could not have fathomed.
As a planetary body Mars shares the most geological similarities to the Earth within our
solar system. Therefore, it should come as no surprise that the interest of astrobiologists has
focused on the potential of Mars to currently or in the past have hosted life. Research projects
center their attention on analyzing data to assess the potential viability of life on Mars, that is, its
potential habitability. Pictures were taken during the first mission revealing the existence of
stratified rocks that made up systems of hills and canyons. Likewise, on Earth, stratification
occurs due to erosion caused by water flow that creates the conditions for fossil preservation
with water content. (KQED, 2014)
The existence of water on Mars at least a few billion years ago is now part of the
scientific mainstream and viewed as irrefutable. The reasons are simple and evident in the
photographs: stratified rocks scattered around the equator of the red planet can be seen in
canyons and craters. According to Michael Meyer of NASA's biological star program, "These
photographs suggest that the water remained for a long period of time" (Squyres, 2005). While
the period in which water existed on Mars was not sufficient for the development of intelligent
life, it could very well have served to allow for microscopic life to thrive. For example, bacteria
might have existed because it is capable of living under extraordinarily high and low
SEARCHING FOR LIFE
temperatures. This water may have helped them spread and acclimatize along the lakes that may
The Global Surveyor probe has managed to take around 85,000 photographs, 500 million
laser measurements, hundreds of millions of infrared profiles and hundreds of millions of
gigabytes of information that have been analyzed by NASA since the beginning of the program.
The program has not yet detected the presence of intelligent life on Mars. While a civilization
like ours has yet to be discovered on the planet most similar to ours, it may harbor at least some
of the same microscopic life that is found on Earth. Mars is a planet with scarce water, no ozone
layer, inadequate oxygen, and an electromagnetic field much weaker than Earth's. If biosystems
ever existed on Mars, these may no longer exist. The hope of finding traces of ancient life on
Mars has dropped to almost zero because scientists have concluded from the Martian meteorite
review that Mars has been frozen for about four billion years. The most propitious moment for
the appearance of biosystems in our Solar System happened about 3.5 billion years ago when
Mars was already an icy planet.
Second, we have Saturn’s Moon Enceladus. It has surpassed Mars as the best candidate to
host extraterrestrial life after the discovery of a hidden ocean inside. Few places in the Solar
System are as exciting and intricate as Saturn is. Saturn has 200 moons (more than 60 with
secure orbits). (Parkinson, 2008) Enceladus is one of the innermost moons of Saturn in orbit, the
14th furthest number on the planet. It is located about 2 billion kilometers away from Earth. It
stands out for having a surface temperature below 200 degrees Celsius (NASA, 2017), a higher
temperature than any other place besides Earth. Hypothetical life on Enceladus would have had
to develop and adapt to living in complete darkness.
SEARCHING FOR LIFE
NASA's Cassini spacecraft discovered that there is a region 300 km in diameter with an
underground ocean of liquid water near the south pole of Enceladus. From there, geysers eject
water jets toward the surface. The Cassini probe is capable of capturing high-precision
photographs, recording subtle variations in the satellite’s mass, and measuring the mass
distribution of the moon itself. Scientists noticed that Enceladus did not have enough material on
the surface to have obtained the measurements it obtained concerning gravity. Therefore, it is
practically a fact that Enceladus keeps an ocean in a liquid state and hidden beneath the surface,
which would explain the intense gravity recorded by the probe. (NASA, 2017)
According to Parkinson, the ocean of Enceladus would be between 18 and 24 km below
the thick and frozen surface. The results of the probe show that surface fissures expel large
organic molecules rich in carbon and hydrogen necessary for life. The presence of large complex
molecules, together with liquid water and hydrothermal activity, reinforces the hypothesis that
the Enceladus ocean can be a habitable environment for life. (Parkinson et al., 2008) Enceladus
is so white that it absorbs very little sunlight causing it to be -200 C° (NASA, 2017). This,
however, is only the case for its exterior as it has an internal heat source that causes the geysers
at the south pole of Enceladus. The presence of water-soluble organic particles does not
guarantee that there are life forms in Enceladus, but it is a reliable indicator that it does. The
discovery should encourage scientists to send new problems aimed at analyzing Enceladus’
Lastly, we have our very own planet as a reference point for the development of life in
hostile environments. Scientists have discovered hundreds of hydrothermal sources around the
world. The first vent was discovered in 1977 by a team that working on the Galapagos coast. The
discovery was a revolution for scientific thinking about how and where life could exist. It
SEARCHING FOR LIFE
provided strong evidence for the idea that life appeared on earth as a result of hydrothermal
vents. (Martin, 2008) The hydrothermal sources are usually found near places with oceanic
volcanic activity and are rich in chemical elements that can create complex organic reactions. A
very hostile environment surrounds these sources since these generally do not have enough light.
Due to their location in deep areas of the ocean, the pressure is very high. The steam columns
emanating from the holes can contain toxic chemicals including hydrogen sulfide, poisonous to
many animals. Nonetheless, these vents manage to house a large number of different creatures,
such as tubeworms and crabs.
A new type of bacteria has been discovered that uses toxic gases as a source of energy.
The same bacteria serives as a food source for crabs, clams and tube worms. Some of the world's
oldest fossils, discovered by a team led by UCL, originated from these underwater vents.
(Martin, 2008) Researchers have also hypothesized that deep-sea hydrothermal vents are not
exclusive to Earth. Some other planets like cold moons of Jupiter and Saturn might have similar
hydrothermal vents. Different types of hydrothermal sources exist in the southern Gulf of
California: black fumaroles, carbonate fireplaces and hydrothermal vents. Each environment
sustains its unique animal community. (Zierenberg, 2000)
Life on other planets inevitably leads us to consider the origin of life and when we
consider the origin of life, the study of the history of the matter is inevitable. 90% of the Earth’s
ocean floor has not yet been explored, and there are species whose habitats we do not yet
understand. Just like in our solar system, there is a wide range of organic compounds within
meteorites. NASA has pointed out the possibility of finding extraterrestrial life is less likely than
what we believe since finding a space that has all the ideal conditions for life has proven
SEARCHING FOR LIFE
difficult. Millions of years and suitable conditions are necessary to generate microorganisms and
species on a planet.
Ironically Saturn and Jupiter have served a pivotal role in allowing the existence of life
on Earth by blocking it from the impact of asteroids. Although it has not yet been possible to
confirm the existence of extraterrestrial life, NASA has not given up on the mission to explore
new planets with the ideal conditions to support life. Areas of planet Earth that support life
despite what would otherwise be deemed inhabitable conditions provides strong evidence of the
existence of microorganisms in Enceladus and Mars. We conclude that the needs of life are
liquid water and energy sources, which are quite common in the Solar System. We might be
closer to new life, but bacteria might die before we discover it; that is the nature and mystery of
life. Space exploration is one of the great adventures of our time and, for decades, scientists and
astronomers have searched planets capable of harboring life.
SEARCHING FOR LIFE
Baross, J. A., & Hoffman, S. E. (1985). Submarine hydrothermal vents and associated gradient
environments as sites for the origin and evolution of life. Origins of Life and Evolution of
the Biosphere, 15(4), 327-345.
KQED QUEST. (2014, November 18). Searching for Life on Mars. Retrieved February 11,
2020, from https://www.youtube.com/watch?v=LHMQyQ_YwL8&feature=youtu.be
Martin, W., Baross, J., Kelley, D., & Russell, M. J. (2008). Hydrothermal vents and the origin of
life. Nature Reviews Microbiology, 6(11), 805-814.
McKay, C. P., Porco, C. C., Altheide, T., Davis, W. L., & Kral, T. A. (2008). The possible origin
and persistence of life on Enceladus and detection of biomarkers in the plume.
Astrobiology, 8(5), 909-919.
McKay, D. S., Gibson, E. K., Thomas-Keprta, K. L., Vali, H., Romanek, C. S., Clemett, S. J., ...
& Zare, R. N. (1996). Search for past life on Mars: possible relic biogenic activity in
Martian meteorite ALH84001. Science, 273(5277), 924-930.
NASA Jet Propulsion Laboratory. (2017, April 13). NASA: Ingredients for Life at Saturn’s
Moon Enceladus. Retrieved February 12, 2020, from
NASA. (2017, April 13). Ingredients for Life at Enceladus. Retrieved February 12, 2020, from
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Ocean Explore Gov. (2017, August 25). Hydrothermal Vents: 2016 Deepwater Exploration of
the Marianas. Retrieved February 12, 2020, from
Parkinson, C. D., Liang, M. C., Yung, Y. L., & Kirschivnk, J. L. (2008). Habitability of
Enceladus: planetary conditions for life. Origins of Life and Evolution of Biospheres,
Zierenberg, R. A., Adams, M. W., & Arp, A. J. (2000). Life in extreme environments:
Hydrothermal vents. Proceedings of the National Academy of Sciences, 97(24), 1296112962.
Running head: EARTH LIFE FORMS
EARTH LIFEFORMS SURVIVAL ON MARS
EARTH LIFE FORMS
The potential of Mars supporting life is contentious that has fascinated scientists for
years. Other than the proximity to Earth, the planet also bears some resemblance that points
towards the possibility of supporting life. Some evidence suggests that during the ancient
Noachian era, the planet contained liquid water that could have supported the survival of
microorganisms. National Space Agency (NASA) mentioned that the Curiosity rover sent
information about discovering organic compounds in rock samples from Mars (Kral et al., 2016).
The rover also found boron on the planet, which is a precursor of prebiotic chemistry. Such
findings point towards the possibility of some organisms from Earth to thrive under such
conditions. Although the surface of Mars is covered by ionizing radiation, scientists believe that
the planet's subsurface may be harboring frozen water, which is a crucial element in supporting
life. Through the ability to withstand conditions of low light, salt toxicity, fewer nutrients, and
extreme temperature changes, methanogens, cyanobacteria, and lichens have the potential to
exist on Mars.
Methanogens could survive on Mars for their anaerobic and non-photosynthetic traits.
The features could enable them to subsist under the subsurface of Mars. The organisms can also
tolerate perchlorate salt concentrations. Methanogens are classified under the domain Archae.
They are known to utilize hydrogen as their reserve of energy and carbon (IV) Oxide as their
source of carbon. They break down and release natural gas. On Erath, these microorganisms can
be found in swamps; however, they can also be found in guts of herbivores and decaying matter.
The evidence to back the claim regarding the ability of methanogens to withstand
Martian conditions can be found in published studies. Multiple studies show different
perspectives on how particular methanogen species are suited for the conditions on Mars.
One study focused on Methanothermobacter wolfeii and Methanobacterium formicicum
established that the two species could endure the Martian freeze-thaw cycles as replicated in the
lab (Mickol & Kral, 2017). The two species were tried for their capability to tolerate the extreme
Martian freeze-thaw phases that are significantly lower than their ideal growth temperatures of
37oC and 55oC for M. formicicum and M. wolfeii, respectively. The two species were selected
due to their thermophile and hyperthermophile features, respectively. Although the low
temperatures on Mars may limit the growth of these methanogens, they can survive. From the
experiment, the microorganisms were able to resume growth and metabolism upon being
subjected to their respective growth temperatures (Mickol & Kral, 2017). The findings show how
these organisms can adapt to the extreme conditions on Mars.
The temperature on the Martian surface fluctuates extensively, often ranging between 90oC and 27oC in a single Martian day. As such, the existence of any life form would be
expected to withstand the wide temperature range (Mickol & Kral, 2017). Methanogens are
among the leading candidates that could survive the extreme temperature range. Another study
by Kral et al. (2016) explored the capability of methanogens to exist in perchlorate. The research
was inspired by the Curiosity rover’s confirmation that the Mars surface contained perchlorate.
The experiment was executed by testing the capability of methanogen species to tolerate
different concentrations of perchlorate solution. The microorganisms tested included
Methanosarcina barkeri and Methanobacterium formicicum as well as Methanothermobacter
wolfeii. The researchers used methane production to assess methanogen growth. The findings
EARTH LIFE FORMS
indicate that all methanogens released significant levels of methane when subjected to a
maximum of 1.0 percent perchlorate (Kral et al., 2016). The evidence on the survival capability
of methanogens is strong. Most of the study findings are based on laboratory experiments that
subjected methanogens to Mars-like conditions replicated in the laboratory. Furthermore, there is
an extensive collection of published work that supports the claim.
Cyanobacteria are among the Earth's most robust life forms. They lack specialized
compartments; instead, their genetic material is spread all over inside the cell. Cyanobacteria rely
on molecules such as chlorophyll and phycocyanin to gather light energy. Another unique feature
of these life forms is the ability to thrive in conditions with high oxygen and low oxygen
concentrations (Bothe, 2019). Some cyanobacteria species are tolerant of extreme conditions
such as salt toxicity, high temperatures as well UV-irradiation. The tolerance features and the
ability to photosynthesize under low light determine cyanobacteria’s capability to survive
According to a study by Bothe (2019), certain cyanobacteria, particularly from the genus
Chroococcidiopsis, are exceptional because if they have minimal nutrient requirements. The
species also has a unique adaptation that enables it to meet its nitrogen requirement through
nitrogen fixation. Rather than rely on water for photosynthesis, cyanobacteria can use molecular
nitrogen gas. Furthermore, the evidence highlights a crucial feature that could enable
cyanobacteria to withstand extreme conditions on Mars (Bothe, 2019). The Chroococcidiopsis is
tolerant to desiccation. On Earth, most of these organisms have been discovered in harsh desert
conditions marked by low precipitation. They safeguard themselves against intense irradiation by
dwelling under the rocks in an endolithic manner of life. Additionally, Chroococcidiopsis can
also withstand salt toxicity, as evidenced by the species found in salt crystals. Scholars believe
that moisture that condenses on the halite crystals is adequate to support their existence.
The rocky material close to the surface of Mars contains silica, which could be conducive
for the growth of organisms such as cyanobacteria. Additionally, Chroococcidiopsis strains do
not rely on a supply of organic nitrogen. Instead, these life forms meet the requirement for
nitrogen via nitrogen fixation, where atmospheric dinitrogen molecule is converted to
ammonium ion under the influence of nitrogenase enzyme (Bothe, 2019). Desiccation tolerance
is another trait that could enable the microorganisms to thrive under desert-like conditions on the
Mars surface. Chroococcidiopsis minimize both photosynthesis and respiration in the onset of
drought. They resume normal photosynthesis once their habitat receives adequate precipitation.
Poikilohydrous behavior is a vital feature that would aid the survival of cyanobacteria on Mars.
Furthermore, the evidence highlights Chroococcidiopsis thermalis ability to carry out
photosynthesis under low light conditions. The scientists established that the cyanobacterium
species could continue to photosynthesize beyond the limit 700 nanometers wavelength (Bothe,
2019). The characteristics also support the claim regarding reliance on less biological fuel.
Most of the evidence points towards Chroococcidiopsis as the cyanobacterial that is
capable of withstanding the harsh conditions on Mars. Nonetheless, the claim about
cyanobacteria is still controversial. Scientists are yet to establish the strain combinations with the
best traits to tolerate the varying extreme conditions on Mars. Furthermore, the evidence does not
EARTH LIFE FORMS
highlight the physiological, molecular as well as biochemical features that allow cyanobacteria
molecules to dwell in specific desert habitats.
Lichens are among the most robust organisms on Earth. They can exist on trees, rock
surfaces as well as walls. Lichens survive through partnerships as a fungal cell interjoined with
an algae or cyanobacteria cell. The combination makes it possible for lichens to tolerate
extreme conditions and desiccation. They have been discovered at different altitudes as well as
Polar Regions which closely resemble conditions on Mars.
Scientists describe lichens as ‘extremophiles’ due to their capability to tolerate some
hostile conditions on Earth, particularly in habitats such as rocks, deserts as well as dry valleys.
Nonetheless, lichens exist as a composite life form (Armstrong, 2019). Their survival relies on
the presence of a wide range of organisms, including cyanobacteria and multiple types of fungi.
Evidence highlights that lichens have most features to qualify as a stress-tolerant organism. They
have low nutrient requirements, longevity, slow growth, as well as adaptation to withstand
desiccation (Armstrong, 2019). The ability to tolerate such harsh conditions entails functional
and structural adaptations as well as the transition in ecological behavior. The lichen structure
encompasses a fungal tissue. Cya ...
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